[docs] Add applies_to labels for 9.1.0 (#17864) (#17981)

* add applies_to badge to changes introduced in #17351

* add applies_to badge to changes introduced in #17759

* reorder list items

* use 9.0.1 not 9.1.0

* Update docs/reference/keystore.md



---------


(cherry picked from commit aed28eb)

Co-authored-by: Colleen McGinnis <[email protected]>
Co-authored-by: Karen Metts <[email protected]>

Author: 3 people

docs/reference/keystore.md

@@ -136,7 +136,10 @@ bin/logstash-keystore add ES_USER ES_PWD
 When prompted, enter a value for each key.
 
 ::::{note}
-Key values are limited to ASCII letters (`a`-`z`, `A`-`Z`), numbers (`0`-`9`), underscores (`_`), and dots (`.`); they must be at least one character long and cannot begin with a number.
+Key values are limited to:
+
+* {applies_to}`stack: ga 9.0.1` ASCII letters (`a`-`z`, `A`-`Z`), numbers (`0`-`9`), underscores (`_`), and dots (`.`). Key values must be at least one character long and cannot begin with a number.
+* {applies_to}`stack: ga 9.0.0` ASCII characters including digits, letters, and a few special symbols.
 ::::
 
 

docs/reference/persistent-queues.md

@@ -81,7 +81,8 @@ If you want to define values for a specific pipeline, use [`pipelines.yml`](/ref
 
     To avoid losing data in the persistent queue, you can set `queue.checkpoint.writes: 1` to force a checkpoint after each event is written. Keep in mind that disk writes have a resource cost. Setting this value to `1` ensures maximum durability, but can severely impact performance. See [Controlling durability](#durability-persistent-queues) to better understand the trade-offs.
 
-
+`queue.checkpoint.interval` {applies_to}`stack: deprecated 9.1`
+:   Sets the interval in milliseconds when a checkpoint is forced on the head page. Default is `1000`. Set to `0` to eliminate periodic checkpoints.
 
 ## Configuration notes [pq-config-notes]